Dataset for: Breeding populations of Marbled Godwits and Willets have high annual survival and strong site fidelity to managed wetlands

The Prairie Pothole Region of central Canada supports a diverse community of breeding waterbirds but many species have declining populations and the demographic mechanisms driving the declines remain unknown. We conducted a 7-year field study during 1995–2001 to investigate the demographic performance of Marbled Godwits (Limosa fedoa) and Willets (Tringa semipalmata) breeding in managed wetlands near Brooks, Alberta. Mark-recapture analyses based on Cormack-Jolly-Seber models revealed that the annual rates of apparent survival for Marbled Godwits (phi-hat = 0.934 ± 0.015SE) and Willets (phi-hat = 0.849 ± 0.018SE) are among the highest rates of survivorship reported for any breeding or nonbreeding population of large-bodied shorebirds. Our estimates of life expectancy for males were comparable to longevity records in godwits (E-hat = 17.3 years ± 5.8SE vs. 25-29+ years) and Willets (E- hat = 7.7 ± 1.5SE vs. 10+ years). The two species both showed strong breeding site fidelity but differed in rates of mate fidelity.  Pairs that reunited and males that switched mates usually nested <300 m from their previous nests whereas females that switched mates usually moved longer distances >1.1 to 1.5 km. Returning pairs usually reunited in godwits (85%) but not in Willets (28%), possibly because of species differences in adult survival or patterns of migration. Baseline estimates of annual survival for banded-only birds will be useful for evaluating the potential effects of new tracking tags or the environmental changes that have occurred during the past 20 years. Conservation strategies for large-bodied shorebirds should be focused on reduction of exposure to anthropogenic mortality because low rates of natural mortality suggest that losses to collisions at breeding sites or harvest at nonbreeding areas are likely to cause additive mortality.

Methods
Dates of data collection: We conducted a 7-year breeding study (1995–2001) of Marbled Godwits and Western Willets in Alberta.  Fieldwork at Kitsim was conducted by 2–6 shorebird observers from late April to mid-July with 37 to 67 days of nest searching, monitoring and captures in 1995–2000, and 18 days of resighting effort in 2001. 

Geographic locations of data collection: Fieldwork was conducted at the Kitsim wetland complex, located 13 km southwest of Brooks, Alberta (50.5042 deg N, 112.0459 deg W).  The core study area was northwest of the intersection of highways 539 and 36 and had an area of 21.6 km2 (3.3 km W-E by 6.5 km N-S).  Additional monitoring was conducted on two smaller patches to the west (2.7 km2) and to the southeast (4.4 km2) of the core study area. 

Study species: The two study species were Marbled Godwits (Limosa fedoa) and Willets (Tringa semipalmata). The populations studied in Alberta were of the midcontinental subspecies (L. f. fedoa, and T. s. inornata).